Ring member shift mechanism and lens group shift mechanism

ABSTRACT

A shift mechanism includes first and second ring bodies which are relatively rotatable; a shift cam surface formed on the first ring body on an end surface thereof which faces the second ring body, the shift cam surface being inclined with respect to a circumferential direction of the first ring body; a follower projection formed on the second ring body for engaging with the shift cam surface; and a rotating mechanism for relatively rotating the first and second ring bodies. The shift cam surface and the follower projection are arranged to move the first and second ring bodies toward and away from each other in the axial direction as the first and second ring bodies are relatively rotated. An annular rib is formed along the circumference of the first ring body outside the shift cam surface over the follower projection of the second ring body.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application relates to the following U.S. PatentApplications, all filed concurrently herewith on Sep. 24, 2001, and allof which are expressly incorporated herein by reference in theirentireties: “ZOOM LENS MECHANISM” having attorney docket No. P21180,“ZOOM LENS MECHANISM” having attorney docket No. P21181,“ECCENTRICITY-PREVENTION MECHANISM FOR A PAIR OF LENS-SUPPORTING RINGS”having attorney docket No. P21182, “REDUCTION GEAR MECHANISM” attorneydocket No. P21183, “LENS BARREL” having attorney docket No. P21185,“LENS BARREL” having attorney docket No. P21186, “LENS BARREL” havingattorney docket No. P21187, “LENS BARREL” having attorney docket No.P21188, “ZOOM LENS BARREL” having attorney docket No. P21190, and “LENSBARREL” having attorney docket No. P21192, each naming as inventorsHiroshi NOMURA et al.; and “LENS DRIVE CONTROL APPARATUS FOR ZOOM LENSSYSTEM HAVING A SWITCHING LENS GROUP” having attorney docket No. P21189and naming as inventor Norio NUMAKO.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a mechanism for shifting ringbodies toward and away from each other and a mechanism for moving lensgroups. In particular, the present invention relates to a mechanism formoving ring bodies or lens groups via an end-faced cam surface.

[0004] 2. Description of the Related Art

[0005] The assignee of the present application has proposed anunprecedented zoom lens system that meets the contradictory demands ofhigh zoom ratio and miniaturization (U.S. patent application Ser. No.09/534,307, Japanese Patent Application No. Hei 11-79572). This zoomlens system has the following characteristics: it includes a pluralityof movable lens groups for varying the focal length; at least one of thelens groups is a switching lens group which includes two sub-lensgroups, one of the sub-lens groups being a movable sub-lens group thatcan be selectively positioned at either one movement extremities in theoptical axis direction with respect to the other sub-lens group; themovable sub-lens group of the switching lens group is positioned at anextremity of a short-focal-length zooming range, from the short focallength extremity to an intermediate focal length, and at the oppositeextremity of a long-focal-length zooming range, from the intermediatefocal length to a long focal length extremity; and zoom paths of theswitching lens group and the other lens groups are discontinuous at theintermediate focal length and are defined to focus on a predeterminedimage plane corresponding to the position of the movable sub-lens groupThere may be one or more intermediate focal lengths.

[0006] When selecting or designing a mechanism for moving ring bodies(such as a lens group frames) with emphasis on a particular virtue ofthe mechanism, e.g., simplicity, the same mechanism may have otherdrawbacks, e.g., the simple mechanism may not have the preferred amountor optimum amount of strength, or the simple mechanism may have gapsthrough which light can enter the system. It may not be desirable,however, to provide a separate member for reinforcement and/orlight-shielding purposes in view of space required to provide suchconstruction as well as in view of the manufacturing cost.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a shiftmechanism as well as a lens group shift mechanism that achieves improvedstrength and light-shielding ability without sacrificing simpleconstruction.

[0008] In order to achieve the above-mentioned object, a shift mechanismfor shifting two ring members is provided, the shift mechanism includinga first ring body and a second ring body which can be rotated relativeto each other about a common axis, at least one of the first and secondring bodies being movable in a direction of the common axis; a shift camsurface formed on the first ring body on an end surface thereof whichfaces the second ring body, the shift cam surface being inclined withrespect to a circumferential direction of the first ring body; afollower projection formed on the second ring body for engaging with theshift cam surface; and a rotating mechanism for rotating the first andsecond ring bodies relative to each other. The shift cam surface and thefollower projection are arranged to move the first and second ringbodies toward and away from each other in the axial direction as thefirst and second ring bodies are rotated relative to each other. Anannular rib is formed along the circumference of the first ring bodyradially outside the shift cam surface to extend toward the second ringbody over the follower projection of the second ring body.

[0009] Preferably, an inner surface of the annular rib of the first ringbody is slidably in contact with a portion of an outer surface of thesecond ring body.

[0010] In an embodiment, the follower projection is formed on the secondring body on one end surface thereof which faces the first ring body,and a second annular rib, which differs from the annular rib of thefirst ring body, is formed along the circumference of the second ringbody radially inside the follower projection to extend toward the firstring body.

[0011] Preferably, the first and second ring bodies include a firstsub-lens group frame and a second sub-lens group frame for supporting afirst sub-lens group and a second sub-lens group, respectively, thefirst and second sub-lens groups functioning optically in a mutuallyclose position and in a mutually distant position, with respect to theoptical axis thereof.

[0012] Preferably, one of the first and second ring bodies includes afocusing lens support member for supporting a focusing lens group so asto move in the axial direction; and the other of the first and secondring bodies includes an actuator ring that can rotate relative to thefocusing lens support member, the rotation of the actuator ring causingthe focusing lens support member to move in the axial direction via theshift cam surface and the follower projection.

[0013] Preferably, the focusing lens support member includes a firstsub-lens group frame and a second sub-lens group frame which support afirst sub-lens group and a second sub-lens group, respectively, and areable to rotate and move in the axial direction with respect to eachother, the first and second sub-lens groups functioning optically in amutually close position and in a mutually distant position, with respectto the optical axis thereof.

[0014] According to another aspect of the present invention, a lensdisplacement mechanism is provided, including a first sub-lens group anda second sub-lens group functioning optically in a mutually closeposition and in a mutually distant position, with respect to the opticalaxis thereof; a first sub-lens group frame and a second sub-lens groupframe which support the first sub-lens group and the second sub-lensgroup, respectively, the first and second sub-lens group frames beingrotatable about a common axis and movable in a direction of the axis,with respect to each other; a shift cam surface formed on the firstsub-lens group frame on an end surface thereof which faces the secondsub-lens group frame, the shift cam surface being inclined with respectto a circumferential direction of the first sub-lens group frame; ashift follower projection formed on the second sub-lens group frame forengaging with the shift cam surface; and an actuator ring for rotatingthe first and second sub-lens group frames relative to each other. Theshift cam surface and the shift follower projection are arranged to movethe first and second sub-lens group frames to the mutually closeposition and to the mutually distant position as the first and secondsub-lens group frames are rotated relative to each other. An annular ribis formed along the circumference of the first sub-lens group frameradially outside the shift cam surface to extend toward the secondsub-lens group frame over the shift follower projection of the secondsub-lens group frame.

[0015] Preferably, an inner surface of the annular rib of the firstsub-lens group frame is slidably in contact with part of an outersurface of the second sub-lens group frame.

[0016] Preferably, the shift follower projection is formed on the secondsub-lens group frame on one end surface thereof which faces the firstsub-lens group frame, and a second annular rib which differs from theannular rib of the first sub-lens group frame is formed along thecircumference of the second sub-lens group frame radially inside theshift follower projection to extend toward the first sub-lens groupframe.

[0017] Preferably, the first and second sub-lens groups form one of aplurality of variable lens groups of a zoom lens system which are movedin the optical axis direction during zooming, the first and secondsub-lens groups serving as a focus lens group when in the mutually closeposition and when in the mutually distant position. A focusing mechanismis provided for moving the first sub-lens group frame and the secondsub-lens group frame to the mutually close position and to the mutuallydistant position in the optical axis direction while maintaining thedistance between the sub-lens group frames.

[0018] Preferably, the focusing mechanism includes a supporting barrelfor supporting the first sub-lens group frame and the second sub-lensgroup frame, the first sub-lens group frame being supported in a mannerthat allows the first sub-lens group frame to move in the optical axisdirection and prevents rotation thereof, the second sub-lens group framebeing supported in a manner that allows the second sub-lens group frameto rotate between two rotational extremities over a predetermined angleand allows linear movement thereof in the optical axis direction, whilepreventing rotation thereof, at two rotational extremities thereof, eachof the two rotational extremities corresponding to the mutually closeposition and the mutually distant position; a focus cam surface providedon the actuator ring on an end surface thereof which faces the secondsub-lens group frame, the focus cam surface being inclined with respectto a circumferential direction of the actuator ring; and a focusingfollower projection provided on the second sub-lens group frame forengaging with the focus cam surface at one of the two rotationalextremities, the focusing follower projection being different from theshift follower projection for engaging with the shift cam surface of thefirst sub-lens group frame. The focus cam surface and the focusingfollower projection of the second sub-lens group frame are arranged soas to move the second sub-lens group frame in the optical axis directionas the actuator ring is rotated.

[0019] Preferably, a second annular rib which differs from the annularrib of the first sub-lens group frame is formed along a circumference ofthe actuator ring radially outside the focus cam surface to extendtoward the second sub-lens group frame over the focusing followerprojection of the second sub-lens group frame.

[0020] The present disclosure relates to subject matter contained inJapanese Patent Application No. 2000-289614 (filed on Sep. 22, 2000)which is expressly incorporated herein in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a schematic drawing of a first embodiment of a zoom lenssystem having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0022]FIG. 2 is a schematic drawing of a second embodiment of a zoomlens system having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0023]FIG. 3 is a schematic drawing of a third embodiment of a zoom lenssystem having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0024]FIG. 4 is a schematic drawing of a fourth embodiment of a zoomlens system having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0025]FIG. 5 is a schematic drawing of a fifth embodiment of a zoom lenssystem having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0026]FIG. 6 is a schematic drawing of a sixth embodiment of a zoom lenssystem having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0027]FIG. 7 is a schematic drawing of a seventh embodiment of a zoomlens system having switching lens groups and the fundamental zoom paththereof, to which the present invention is applied.

[0028]FIG. 8 shows one example of stopping positions of the lens groupswhen a photographic operation is carried out, to which the presentinvention is applied.

[0029]FIG. 9A shows an example of the stopping positions of FIG. 8 andan example of an actual zoom path of the lens groups, to which thepresent invention is applied.

[0030]FIGS. 9B and 9C depict an additional schematic view of theconcepts shown in FIGS. 8 and 9A.

[0031]FIG. 10 is a cross-sectional view showing an embodiment of a zoomlens barrel which includes the zoom lens systems having switching lensgroups shown in FIGS. 1, 8 and 9.

[0032]FIG. 11 is a developed view of an inner surface of a cam ring ofthe zoom lens barrel of FIG. 10 showing an exemplary arrangement of camgrooves.

[0033]FIG. 12 is an exploded perspective view showing components of aswitching lens group frame of the zoom lens barrel.

[0034]FIG. 13 is an exploded perspective view showing some of thecomponents of the switching lens group frame of the zoom lens barrel.

[0035]FIG. 14 is a perspective view showing a different assembly of someof the components of the switching lens group frame of the zoom lensbarrel.

[0036]FIG. 15 is a cross-sectional view of an upper half of theswitching lens group in which a first sub-lens group and a secondsub-lens group are in a mutually distant position at the wide-angleextremity.

[0037]FIG. 16 is a cross-sectional view of an upper half of theswitching lens group in which the first sub-lens group and the secondsub-lens group are in a mutually close position at the telephotoextremity.

[0038]FIG. 17A is an exploded view in which components are exploded inthe optical axis direction, wherein the first sub-lens group and thesecond sub-lens group are in the mutually distant position at thewide-angle side and are focused on an object at infinity.

[0039]FIG. 17B is a developed view showing the components of FIG. 17A inactual engagement.

[0040]FIG. 18A is an exploded view in which components are exploded inthe optical axis direction, wherein the first sub-lens group and thesecond sub-lens group are in the mutually distant position at thewide-angle side and are focused on an object at a minimum distance.

[0041]FIG. 18B is a developed view showing the components of FIG. 18A inactual engagement.

[0042]FIG. 19A is an exploded view in which components are exploded inthe optical axis direction, wherein the first sub-lens group and thesecond sub-lens group are in the mutually close position at thetelephoto side and are focused on an object at infinity.

[0043]FIG. 19B is a developed view showing the components of FIG. 19A inactual engagement.

[0044]FIG. 20A is an exploded view in which components are exploded inthe optical axis direction, wherein the first sub-lens group and thesecond sub-lens group are in the mutually close position at thetelephoto side and are focused on an object at a minimum distance.

[0045]FIG. 20B is a developed view showing the components of FIG. 20A inactual engagement.

[0046]FIG. 21 is an exploded view illustrating how the mutually closeposition of the first sub-lens group and the second sub-lens group onthe telephoto side switches to/from the mutually distant position on thewide-angle side via the rotation of an actuator ring.

[0047]FIG. 22 illustrates how focusing is carried out by the actuatorring.

[0048]FIG. 23 is an enlarged expanded view showing a face cam of a firstsub-lens group frame.

[0049]FIG. 24 is an enlarged developed view showing the relationship ofthe first sub-lens group frame, the second sub-lens group frame, and theactuator ring with respect to a front shutter retaining ring.

[0050]FIG. 25 is a front view showing the relationship between the firstsub-lens group frame and the front shutter retaining ring when viewed ina direction of the arrows indicated by a line XXV-XXV in FIG. 14.

[0051]FIG. 26 is a partially enlarged view showing an encircled portionindicated by XXVI in FIG. 25.

[0052]FIG. 27 is a front view showing the relationship between thesecond sub-lens group frame and the front shutter retaining ring whenviewed in a direction of the arrows indicated by the line XXVII-XXVII inFIG. 14.

[0053]FIG. 28 is a partially enlarged view showing an encircled partXXVIII in FIG. 27.

[0054]FIG. 29 is a front view showing an arrangement of reduction gearsof a driving system of the actuator ring, the reduction gears beingretained between the front shutter retaining ring and the gear holdingring.

[0055]FIG. 30 is a developed plan view of FIG. 29.

[0056]FIG. 31 is a block diagram showing a control system of the zoomlens barrel shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] The present invention is applied to a lens barrel as describedbelow, and is suitable for use with a zoom lens system proposed by theassignee of the present application in the U.S. patent application Ser.No. 09/534,307. U.S. patent application Ser. No. 09/534,307 is expresslyincorporated herein by reference in its entirety.

[0058] A so-called end-faced cam is one mechanism for moving ring bodiessuch as a lens group frame, in which a cam surface which is inclinedwith respect to the circumferential direction is formed on an endsurface of one of a pair of ring bodies that can be rotated relative toeach other and a follower projection is provided on the other of thering bodies for engaging the cam surface. While employing such anend-faced cam can provide an advantage of a simple construction of theshift mechanism, it can be desirable with respect to the strength of thering body, having the cam surface, to shape the end surface of the ringbody as a perfect cylinder without having an end-faced cam. When thering bodies that are moved via the end-faced cam are adopted as a lensgroup frame, it is also necessary to prevent light from passing throughthe cam surface area. It may not be desirable, however, to provide aseparate member for reinforcement and/or light-shielding purposes inview of space required to provide such construction as well as themanufacturing cost.

[0059] In the designing of a mechanical structure of a lens barrel foruse in a zoom lens system such as that proposed in the U.S. patentapplication Ser. No. 09/534,307, it is preferred to employ an end-facedcam mechanism of the type described above to make the construction ofthe lens shift mechanism simple. This, however, leaves the problemconcerning the strength and light-shielding ability of the lens shiftmechanism.

[0060] First, embodiments of a zoom lens system with a switching lensgroup proposed in the U.S. patent application Ser. No. 09/534,307 willbe herein described.

[0061]FIG. 1 shows the first embodiment of the zoom lens system. Thezoom lens system includes a positive first variable lens group 10, and anegative second variable lens group 20, in that order from the objectside. The first variable lens group 10 includes a negative first lensgroup L1 (first sub-lens group S1) and a positive second lens group L2(second sub-lens group S2), in that order from the object side. Thesecond variable lens group 20 includes a negative third lens group L3.The second sub-lens group S2 of the first variable lens group 10 isfixed to a first lens group frame 11. The first sub-lens group S1 ismounted on a movable sub-lens group frame 12. The movable sub-lens groupframe 12 is arranged to move in the optical axis direction, by apredetermined distance, along a guide groove 13 which is formed on thefirst lens group frame 11. The first sub-lens group S1 is selectivelymoved to either the object-side movement extremity at which the movablesub-lens group frame 12 comes into contact with the front end of theguide groove 13, or the image-side movement extremity at which themovable sub-lens group frame 12 comes into contact with the rear end ofthe guide groove 13. The third lens group L3 is fixed to a second lensgroup frame 21. A diaphragm D is arranged to move together with thefirst variable lens group 10 (first lens group frame 11). ThroughoutFIGS. 1 through 9, IM indicates an image plane (film surface, and soforth) which is at a predetermined position.

[0062] In the zoom paths according to the first embodiment, the firstvariable lens group 10 (first lens group frame 11) the second variablelens group 20 (second lens group frame 21), and the first sub-lens groupS1 (movable sub-lens group frame 12) move in the following manner:

[0063] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to an intermediate focal length fm, the firstsub-lens group S1 and the second sub-lens group S2 maintain a distanced1 therebetween (first separation space/wide space); and the firstvariable lens group 10 (first lens group frame 11) and the secondvariable lens group 20 (second lens group frame 21) move towards theobject side while mutually changing the distance therebetween.

[0064] [B] At the intermediate focal length fm, the first variable lensgroup 10 and the second variable lens group 20 move towards the imageside at the long focal-length extremity of the short-focal-lengthzooming range Zw; and the first sub-lens group S1 moves to theimage-side movement extremity of the guide groove 13, wherein the firstsub-lens group S1 moves toward the second sub-lens group S2 so that thedistance therebetween is determined by a shorter distance (secondseparation space/narrow space) d2.

[0065] [C] In a long-focal-length zooming range Zt from the intermediatefocal length fm to the long focal length extremity ft, the firstsub-lens group S1 maintains the shorter distance (second separationspace/narrow space) d2 with respect to the second sub-lens group S2; andthe first variable lens group 10 and the second variable lens group 20move towards the object, based on the positions thereof which aredetermined at the intermediate focal length fm, after the first throughthird lens groups L1 through L3 have been moved towards the image side,while changing the distance therebetween.

[0066] The zoom paths for the first variable lens group 10 and thesecond variable lens group 20 are simply depicted as straight lines inFIG. 1. It should be noted, however, that the actual zoom paths are notnecessarily straight lines.

[0067] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 and the second sub-lens group S2,i.e., the first variable lens group 10 (first lens group frame 11)regardless of the zooming range.

[0068]FIG. 2 shows the second embodiment of the zoom lens system. Thezoom lens system includes a positive first variable lens group 10, apositive second variable lens group 20, and a negative third variablelens group 30, in that order from the object side. The first variablelens group 10 includes a positive first lens group L1. The secondvariable lens group 20 includes a negative second lens group L2 (firstsub-lens group S1) and a positive third lens group L3 (second sub-lensgroup S2), in that order from the object side. The third variable lensgroup 30 includes a negative fourth lens group L4. The first lens groupL1 is fixed to a first lens group frame 11. The second sub-lens group S2of the second variable lens group 20 is fixed to a second lens groupframe 21. The first sub-lens group S1 is mounted on a movable sub-lensgroup frame 22. The movable sub-lens group frame 22 is arranged to move,in the optical axis direction, by a predetermined distance, along aguide groove 23 which is formed on the second lens group frame 21. Thefirst sub-lens group S1 is selectively moved to either the object-sidemovement extremity at which the movable sub-lens group frame 22 comesinto contact with the front end of the guide groove 23, or theimage-side movement extremity at which the movable sub-lens group frame22 comes into contact with the rear end of the guide groove 23. Thefourth lens group L4 is fixed to a third lens group frame 31. Adiaphragm D is arranged to move together with the second variable lensgroup 20 (second lens group frame 21).

[0069] In the zoom paths according to the second embodiment, the firstvariable lens group 10 (first lens group frame 11), the second variablelens group 20 (second lens group frame 21), the third variable lensgroup 30 (third lens group frame 31), and the first sub-lens group S1(movable sub-lens group frame 22) move in the following manner:

[0070] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to an intermediate focal length fm, the firstsub-lens group S1 and the second sub-lens group S2 maintain a distanced1 (first separation space/wide space); and the first variable lensgroup 10 (first lens group frame 11), the second variable lens group 20(second lens group frame 21) and the third variable lens group 30 (thirdlens group frame 31) move towards the object side while mutuallychanging the distances therebetween.

[0071] [B] At the intermediate focal length fm, the first variable lensgroup 10, the second variable lens group 20 and the third variable lensgroup 30 are moved towards the image side at the long focal-lengthextremity of the short-focal-length zooming range Zw; and the firstsub-lens group S1 moves to the image-side movement extremity of theguide groove 23, wherein the first sub-lens group S1 moves toward thesecond sub-lens group S2 so that the distance therebetween is determinedby a shorter distance (second separation space/narrow space) d2.

[0072] [C] In a long-focal-length zooming range Zt from the intermediatefocal length fm to the long focal length extremity ft, the firstsub-lens group S1 and the second sub-lens group S2 maintain the shorterdistance d2; and the first variable lens group 10, the second variablelens group 20 and third variable lens group 30 move towards the objectside based on the positions thereof which are determined at theintermediate focal length fm, after the first through fourth lens groups1 through 4 have been moved towards the image side, while changing thedistances therebetween.

[0073] The zoom paths for the first variable lens group 10, the secondvariable lens group 20 and the third variable lens group 30 are simplydepicted as straight lines in FIG. 2. It should be noted, however, thatactual zoom paths are not necessarily straight lines.

[0074] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 and the second sub-lens group S2,i.e., the second variable lens group 20 (second lens group frame 21)regardless of the zooming range.

[0075] Likewise with the first embodiment, the zoom paths arediscontinuous at the intermediate focal length fm; however, a solutionfor continuously forming a correct image plane exists by appropriatelydetermining the positions of the first lens group L1, the first sub-lensgroup S1 (second lens group L2) and the second sub-lens group S2 (thirdlens group L3) and the fourth lens group L4 respectively at the shortfocal length extremity fw, the intermediate focal length fm(discontinuous line) and the long focal length extremity ft. Accordingto such a zoom path, a miniaturized zoom lens system having a high zoomratio can be obtained.

[0076]FIG. 3 shows the third embodiment of the zoom lens system with aswitching lens system. In this embodiment, the first lens group L1 isconstructed so as to have negative refractive power, which is the onlydifference compared with the second embodiment. Apart from thischaracteristic, the third embodiment is substantially the same as thesecond embodiment.

[0077]FIG. 4 shows the fourth embodiment of the zoom lens system with aswitching lens group. The zoom lens system includes a positive firstvariable lens group 10, and a negative second variable lens group 20, inthat order from the object side. The first variable lens group 10includes a negative first lens group L1 (first sub-lens group S1) and apositive second lens group L2 (second sub-lens group S2), in that orderfrom the object side. The second variable lens group 20 includes apositive third lens group L3 (third sub-lens group S3) and a negativefourth lens group L4 (fourth sub-lens group S4), in that order from theobject side.

[0078] The second sub-lens group S2 of the first variable lens group 10is fixed to a first lens group frame 11. The first sub-lens group S1 ismounted on a movable sub-lens group frame 12. The movable sub-lens groupframe 12 is arranged to move in the optical axis direction, by apredetermined distance, along a guide groove 13 which is formed on thefirst lens group frame 11. The first sub-lens group S1 is selectivelymoved to either the object-side movement extremity at which the movablesub-lens group frame 12 comes into contact with the front end of theguide groove 13, or the image-side movement extremity at which themovable sub-lens group frame 12 comes into contact with the rear end ofthe guide groove 13. Similarly, the fourth sub-lens group S4 of thesecond variable lens group 20 is fixed to a second lens group frame 21.The third sub-lens group S3 is mounted on a movable sub-lens group frame22. The movable sub-lens group frame 22 is arranged to move in theoptical axis direction, by a predetermined distance, along a guidegroove 23 which is formed on the second lens group frame 21. The thirdsub-lens group S3 is selectively moved to either the object-sidemovement extremity at which the movable sub-lens group frame 22 comesinto contact with the front end of the guide groove 23, or theimage-side movement extremity at which the movable sub-lens group frame22 comes into contact with the rear end of the guide groove 23. Adiaphragm D is arranged to move together with the first variable lensgroup 10 (first lens group frame 11).

[0079] In the zoom paths according to the fourth embodiment, the firstvariable lens group 10 (first lens group frame 11), the second variablelens group 20 (second lens group frame 21), the first sub-lens group S1,and the third sub lens group S3 move in the following manner:

[0080] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to an intermediate focal length fm, the firstsub-lens group S1 and the second sub-lens group S2 maintain a distanced1 therebetween (first separation space/wide space), and the thirdsub-lens group S3 and the fourth sub-lens group S4 maintain a distanced3 therebetween (first separation space/wide space); and the firstvariable lens group 10 (first lens group frame 11) and the secondvariable lens group 20 (second lens group frame 21) move towards theobject side while mutually changing the distance therebetween.

[0081] [B] At the intermediate focal length fm, the first variable lensgroup 10 and the second variable lens group 20 are moved towards theimage side at the long focal-length extremity of the short-focal-lengthzooming range Zw; and the first sub-lens group S1 moves to theimage-side movement extremity of the guide groove 13, wherein the firstsub-lens group S1 moves toward the second sub-lens group S2 so that thedistance therebetween is determined by a shorter distance (secondseparation space/narrow space) d2, and also the third sub-lens group S3moves toward the fourth sub-lens group S4 so that the distancetherebetween is determined by a shorter distance (second separationspace/narrow space) d4.

[0082] [C] In a long-focal-length zooming range Zt from the intermediatefocal length fm to the long focal length extremity ft, the firstsub-lens group S1 and the second sub-lens group S2 maintain the shorterdistance d2 therebetween, and the third sub-lens group S3 and the fourthsub-lens group S4 maintain the shorter distance d4 therebetween; and thefirst variable lens group 10 and the second variable lens group 20 movetowards the object side based on the positions thereof which aredetermined at the intermediate focal length fm, after the first throughfourth lens groups L1 through L4 have been moved towards the image side,while changing the distance therebetween.

[0083] The zoom paths for the first variable lens group 10 and thesecond variable lens group 20 are simply depicted as straight lines inFIG. 4. It should be noted, however, that the actual zoom paths are notnecessarily straight lines.

[0084] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 and the second sub-lens group S2,i.e., the first variable lens group 10 (first lens group frame 11)regardless of the zooming range.

[0085] Similar to the first through third embodiments, in the fourthembodiment, the zoom paths are discontinuous at the intermediate focallength fm; however, a solution for continuously forming a correct imageplane exists by appropriately determining the positions of the firstsub-lens group S1 (first lens group L1), the second sub-lens group S2(second lens group L2), the third sub-lens group S3 (third lens groupL3), and the fourth sub-lens group S4 (fourth lens group L4),respectively, at the short focal length extremity fw, the intermediatefocal length fm (discontinuous line), and the long focal lengthextremity ft. According to such a zoom path, a miniaturized zoom lenssystem having a high zoom ratio can be obtained.

[0086]FIG. 5 shows the fifth embodiment of the zoom lens system with aswitching lens group. The zoom lens system includes a positive firstvariable lens group 10, and a negative second variable lens group 20, inthat order from the object side. The first variable lens group 10includes a negative first lens group L1 (first sub-lens group S1) and apositive second lens group L2 (second sub-lens group S2), in that orderfrom the object side. The second variable lens group 20 includes apositive third lens group L3 (third sub-lens group S3) and a negativefourth lens group L4 (fourth sub-lens group S4), in that order from theobject side.

[0087] The second sub-lens group S2 of the first variable lens group 10is fixed to a first lens group frame 11. The first sub-lens group S1 ismounted on a movable sub-lens group frame 12. The movable sub-lens groupframe 12 is arranged to move in the optical axis direction, by apredetermined distance, along a guide groove 13 which is formed on thefirst lens group frame 11. The first sub-lens group S1 is selectivelymoved to either the object-side movement extremity at which the movablesub-lens group frame 12 comes into contact with the front end of theguide groove 13, or the image-side movement extremity at which themovable sub-lens group frame 12 comes into contact with the rear end ofthe guide groove 13. Similarly, the fourth sub-lens group S4 of thesecond variable lens group 20 is fixed to a second lens group frame 21.The third sub-lens group S3 is mounted on a movable sub-lens group frame22. The movable sub-lens group frame 22 is arranged to move in theoptical axis direction, by a predetermined distance, along a guidegroove 23 which is formed on the second lens group frame 21. The thirdsub-lens group S3 is selectively moved to either the object-sidemovement extremity at which the movable sub-lens group frame 22 comesinto contact with the front end of the guide groove 23, or theimage-side movement extremity at which the movable sub-lens group frame22 comes into contact with the rear end of the guide groove 23. Adiaphragm D is arranged to move together with the first variable lensgroup 10 (first lens group frame 11).

[0088] In the zoom paths according to the fifth embodiment, the firstvariable lens group 10 (first lens group frame 11) the second variablelens group 20 (second lens group frame 21), the first sub-lens group S1,and the third sub lens group S3 move in the following manner:

[0089] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to a first intermediate focal length fm1, the firstsub-lens group S1 and the second sub-lens group S2 maintain a distanced1 therebetween (first separation space/wide space), and the thirdsub-lens group S3 and the fourth sub-lens group S4 maintain a distanced3 therebetween (first separation space/wide space); and the firstvariable lens group 10 (first lens group frame 11) and the secondvariable lens group 20 (second lens group frame 21) move towards theobject side while mutually changing the distance therebetween.

[0090] [B] At the first intermediate focal length fm1, the firstvariable lens group 10 and the second variable lens group 20 are movedtowards the image side at the long focal-length extremity of theshort-focal-length zooming range Zw; and the first sub-lens group S1moves to the image-side movement extremity of the guide groove 13,wherein the first sub-lens group S1 moved toward the second sub-lensgroup S2 so that the distance therebetween is determined by a shorterdistance (second separation space/narrow space) d2.

[0091] [C] In an intermediate zooming range Zm from the firstintermediate focal length fm1 to a second intermediate focal length fm2,the first sub-lens group S1 and the second sub-lens group S2 maintainthe shorter distance d2, and the third sub-lens group S3 and the fourthsub-lens group S4 maintain the longer distance d3; and the firstvariable lens group 10 and the second variable lens group 20 movetowards the object side based on the positions thereof which aredetermined at the first intermediate focal length fm1, after the firstthrough fourth lens groups L1 through L4 have been moved towards theimage side, while changing the distance therebetween.

[0092] [D] At the second intermediate focal length fm2, the firstvariable lens group 10 and the second variable lens group 20 are movedtowards the image side at the long focal length extremity of theintermediate zooming range Zm; and the third sub-lens group S3 moves tothe image-side movement extremity of the guide groove 23, wherein thethird sub-lens group S3 moves toward the fourth sub-lens group S4 sothat the distance therebetween is determined by a shorter distance(second separation space/narrow space) d4.

[0093] [E] In a long-focal-length zooming range Zt from the secondintermediate focal length fm2 to the long focal length extremity ft, thefirst sub-lens group S1 and the second sub-lens group S2 maintain theshorter distance d2 therebetween, and the third sub-lens group S3 andthe fourth sub-lens group S4 maintain the shorter distance d4therebetween; and the first variable lens group 10 and the secondvariable lens group 20 move towards the object side based on thepositions thereof which are determined at the second intermediate focallength fm2, after the first through fourth lens groups L1 through L4have been moved towards the image side, while changing the distancetherebetween.

[0094] The zoom paths for the first variable lens group 10 and thesecond variable lens group 20 are simply depicted as straight lines inFIG. 5. It should be noted, however, that the actual zoom paths are notnecessarily straight lines.

[0095] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 and the second sub-lens group S2,i.e., the first variable lens group 10 (first lens group frame 11)regardless of the zooming range.

[0096] Similar to the first through fourth embodiments, in the fifthembodiment, the zoom paths are discontinuous at the first intermediatefocal length fm1 and the second intermediate focal length fm2; however,a solution for continuously forming a correct image plane exists byappropriately determining the positions of the first sub-lens group S1(first lens group L1), the second sub-lens group S2 (second lens groupL2), the third sub-lens group S3 (third lens group L3) and the fourthsub-lens group S4 (fourth lens group L4), respectively, at the shortfocal length extremity fw, the first and second intermediate focallengths fm1, fm2 (discontinuous line), and the long focal lengthextremity ft. According to such a zoom path, a miniaturized zoom lenssystem having a high zoom ratio can be obtained.

[0097]FIG. 6 shows the sixth embodiment of the zoom lens system with aswitching lens group. The zoom lens system includes a positive firstvariable lens group 10, and a negative second variable lens group 20, inthat order from the object side. The first variable lens group 10includes a negative first lens group L1 (first sub-lens group S1) and apositive second lens group L2 (second sub-lens group S2), in that orderfrom the object side. The second variable lens group 20 includes apositive third lens group L3 (third sub-lens group S3) and a negativefourth lens group L4 (fourth sub-lens group S4), in that order from theobject side.

[0098] The second sub-lens group S2 of the first variable lens group 10is fixed to a first lens group frame 11. The first sub-lens group S1 ismounted on a movable sub-lens group frame 12. The movable sub-lens groupframe 12 is arranged to move in the optical axis direction, by apredetermined distance, along a guide groove 13 which is formed on thefirst lens group frame 11. The first sub-lens group S1 is selectivelymoved to either the object-side movement extremity at which the movablesub-lens group frame 12 comes into contact with the front end of theguide groove 13, or the image-side movement extremity at which themovable sub-lens group frame 12 comes into contact with the rear end ofthe guide groove 13. Similarly, the fourth sub-lens group S4 of thesecond variable lens group 20 is fixed to a second lens group frame 21.The third sub-lens group S3 is mounted on a movable sub-lens group frame22. The movable sub-lens group frame 22 is arranged to move in theoptical axis direction, by a predetermined distance, along a guidegroove 23 which is formed on the second lens group frame 21. The thirdsub-lens group S3 is selectively moved to either the object-sidemovement extremity at which the movable sub-lens group frame 22 comesinto contact with the front end of the guide groove 23, or theimage-side movement extremity at which the movable sub-lens group frame22 comes into contact with the rear end of the guide groove 23. Adiaphragm D is arranged to move together with the first variable lensgroup 10 (first lens group frame 11).

[0099] In the zoom paths according to the sixth embodiment, the firstvariable lens group 10 (first lens group frame 11), the second variablelens group 20 (second lens group frame 21), the first sub-lens group S1,and the third sub lens group S3 move in following manner:

[0100] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to a first intermediate focal length fm1, the firstsub-lens group S1 and the second sub-lens group S2 maintain a distanced1 therebetween (first separation space/wide space), and the thirdsub-lens group S3 and the fourth sub-lens group S4 maintain a distanced3 therebetween (first separation space/wide space); and the firstvariable lens group 10 (first lens group frame 11) and the secondvariable lens group 20 (second lens group frame 21) move towards theobject side while mutually changing the distance therebetween.

[0101] [B] At the first intermediate focal length fm1, the firstvariable lens group 10 and the second variable lens group 20 are movedtowards the image side at the long focal length extremity of theshort-focal-length zooming range Zw; and the third sub-lens group S3moves to the image-side movement extremity of the guide groove 23, andwherein the third sub-lens group S3 moves toward the fourth sub-lensgroup S4 so that the distance therebetween is determined by a shorterdistance (second separation space/narrow space) d4.

[0102] [C] In an intermediate zooming range Zm from the firstintermediate focal length fm1 to a second intermediate focal length fm2,the first sub-lens group S and the second sub-lens group S2 maintain thelonger distance d1 therebetween, and the third sub-lens group S3 and thefourth sub-lens group S4 maintain the shorter distance d4 therebetween;and the first variable lens group 10 and the second variable lens group20 move towards the object side based on the positions thereof which aredetermined at the first intermediate focal length fm1, after the firstthrough fourth lens groups L1 through L4 have been moved towards theimage side, while changing the distance therebetween.

[0103] [D] At the second intermediate focal length fm2, the firstvariable lens group 10 and the second variable lens group 20 are movedtowards the image side at the long focal length extremity of theintermediate zooming range Zm; and the first sub-lens group S1 moves tothe image-side movement extremity of the guide groove 13, and whereinthe first sub-lens group S1 moves toward the second sub-lens group S2 sothat the distance therebetween is determined by a shorter distance(second separation space/narrow space) d2.

[0104] [E] In a long-focal-length zooming range Zt from the secondintermediate focal length fm2 to the long focal length extremity ft, thefirst sub-lens group S1 and the second sub-lens group S2 maintain theshorter distance d2 therebetween, and the third sub-lens group S3 andthe fourth sub-lens group S4 maintain the shorter distance d4therebetween; and the first variable lens group 10 and the secondvariable lens group 20 move towards the object side based on thepositions thereof which are determined at the second intermediate focallength fm2, after the first through fourth lens groups L1 through L4have been moved towards the image side, while changing the distancetherebetween.

[0105] The zoom paths for the first variable lens group 10 and thesecond variable lens group 20 are simply depicted as straight lines inFIG. 6. It should be noted, however, that the actual zoom paths are notnecessarily straight lines.

[0106] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 and the second sub-lens group S2,i.e., the first variable lens group 10 (first lens group frame 11)regardless of the zooming range.

[0107] Similar to the first through fifth embodiments, in the sixthembodiment, the zoom paths are discontinuous at the first intermediatefocal length fm1 and the second intermediate focal length fm2; however,a solution for continuously forming a correct image plane exists byappropriately determining the positions of the first sub-lens group S1(first lens group L1), the second sub-lens group S2 (second lens groupL2), the third sub-lens group S3 (third lens group L3), and the fourthsub-lens group S4 (fourth lens group L4), respectively, at the shortfocal length extremity fw, the first and second intermediate focallengths fm1, fm2 (discontinuous line), and the long focal lengthextremity ft. According to such a zoom path, a miniaturized zoom lenssystem having a high zoom ratio can be obtained.

[0108]FIG. 7 shows the seventh embodiment of the zoom lens system with aswitching lens group. The zoom lens system includes a positive firstvariable lens group 10, and a negative second variable lens group 20, inthat order from the object side. The first variable lens group 10includes a positive first lens group L1 (first sub-lens group S1), anegative second lens group L2 (second sub-lens group S2) and a positivethird lens group L3 (third sub-lens group S3), in that order from theobject side. The second variable lens group 20 includes a negativefourth lens group L4. The first sub-lens group S1 and the third sub-lensgroup S3 are fixed to a first lens group frame 11. The second sub-lensgroup S2 is mounted on a movable sub-lens group frame 12. The movablesub-lens group frame 12 is arranged to move in the optical axisdirection, by a predetermined distance, along a guide groove 13 which isformed on the first lens group frame 11. The second sub-lens group S2 isselectively moved to either the object-side movement extremity at whichthe movable sub lens group frame 12 comes into contact with the frontend of the guide groove 13, or the image-side movement extremity atwhich the movable sub-lens group frame 12 comes into contact with therear end of the guide groove 13. The fourth lens group L4 of the secondvariable lens group 20 is fixed to a second lens group frame 21. Adiaphragm D is arranged to move together with the first variable lensgroup 10 (first lens group frame 11).

[0109] In the zoom paths according to the seventh embodiment, the firstvariable lens group 10 (first lens group frame 11) the second variablelens group 20 (second lens group frame 21), and the second sub-lensgroup S2 move in the following manner:

[0110] [A] In a short-focal-length zooming range Zw from the short focallength extremity fw to an intermediate focal length fm, the firstsub-lens group S1 and the second sub-lens group S2 maintain a shorterdistance therebetween; however, the second sub-lens group S2 and thethird sub-lens group S3 maintain a longer distance therebetween; and thefirst variable lens group 10 (first lens group frame 11) and the secondvariable lens group 20 (second lens group frame 21) move towards theobject side while changing the distance therebetween.

[0111] [B] At the intermediate focal length fm, the first variable lensgroup 10 and the second variable lens group 20 are moved towards theimage side at the long focal-length extremity of the short-focal-lengthzooming range Zw; and the second sub-lens group S2 moves to theimage-side movement extremity of the guide groove 13, and wherein thesecond sub-lens group S2 moves away from the first sub-lens group S1 andmoves toward the third sub-lens group S3.

[0112] [C] In a long-focal-length zooming range Zt from the intermediatefocal length fm to the long focal length extremity ft, the firstsub-lens group S1 and the second sub-lens group S2 maintain the longerdistance therebetween, and the second sub-lens group S2 and the thirdsub-lens group S3 maintain the shorter distance therebetween; and thefirst variable lens group 10 and the second variable lens group 20 movetowards the object side based on the positions thereof which aredetermined at the intermediate focal length fm, after the first throughfourth lens groups L1 through L4 have been moving towards the imageside, while changing the distance therebetween.

[0113] The zoom paths for the first variable lens group 10 and thesecond variable lens group 20 are simply depicted as straight lines inFIG. 7. It should be noted, however, that the actual zoom paths are notnecessarily straight lines.

[0114] Focusing is performed by integrally moving, in the optical axisdirection, the first sub-lens group S1 through the third sub-lens groupS3, i.e., the first variable lens group 10 (first lens group frame 11)regardless of the zooming range.

[0115] Similar to the first through sixth embodiments, in the seventhembodiment, the zoom paths are discontinuous at the intermediate focallength fm; however, a solution for continuously forming a correct imageplane exists by appropriately determining the positions of the firstsub-lens group S1 (first lens group L1), the second sub-lens group S2(second lens group L2), the third sub-lens group S3 (third lens groupL3), and the fourth lens group L4, respectively, at the short focallength extremity fw, the intermediate focal length fm, (discontinuousline), and the long focal length extremity ft. According to such a zoompath, a miniaturized zoom lens system having a high zoom ratio can beobtained.

[0116] As can be understood from the above description, it is practicalto apply the above-described zoom lens system having switching lensgroups to a photographing lens system of a camera in which thephotographing lens system and a finder optical system are independentlyprovided. Moreover, with respect to each of the first through fourthlens groups L1 through L4, stopping positions at which the lens groupstops upon zooming are preferably determined in a stepwise manner alonga fundamental zoom path, i.e., it is preferable to provide a pluralityof focal-length steps. FIGS. 8 and 9 show zoom lens systems in whichpositions for stopping each lens group are determined in a stepwisemanner along the fundamental zoom paths. Since these zoom lens systemsare the same as that of the first embodiment, identical components areprovided with the same designators. The zoom paths are depicted withfundamental dotted lines; and positions at which the first lens groupframe 11 and the second lens group frame 21 stop are indicated withblack dots along the dotted lines. Further, in FIG. 9A, the dots areconnected by smooth (continuous) curved lines to form an actual zoompath. The actual mechanical structure thereof allows the first lensgroup frame 11 and the second lens group frame 21 to be moved along thesmooth curved lines (actual zoom path).

[0117] In the first through seventh embodiments, each lens group isillustrated as a single lens element; however, a lens group can ofcourse include a plurality of lens elements.

[0118]FIGS. 9B and 9C depict an additional schematic view of theconcepts shown in FIGS. 8 and 9A. It should be noted in the followingexplanation that FIGS. 9B and 9C are schematic in nature (e.g., not toscale and/or not depicting actual shape) and that one skilled in the artwill recognize that the zoom paths are not necessarily straight, and themanner in which the schematics of FIGS. 9B and 9C relate to a designed(zooming) cam groove shape (which will differ depending at least on theoptical configuration). As shown in FIG. 9B and 9C, if, in order toarrange movement in accordance with FIG. 9A, it is determined that onezoom path will be connected in an uninflected line (i.e., essentiallywithout discontinuity or inflection and without switching), then the camring, shape, and orientation of cam groove(s) can be adapted for thispurpose. As shown in FIG. 9B, each of the three fundamental zoom pathscan include a discontinuity. By smoothly connecting one zoom path, inthis case the second zoom path (e.g., depicted in the FIGS. 9B and 9C byshifting all of the zoom paths in the intermediate-to-telephoto range“up” so that the path of the second lens group is connected), it becomespossible to carry out the movements of the combined groups more simply.In this case, it is decided to use “switching” for the first group and asmooth inflection in the second group. As noted, the stepwisemovement/positioning and prohibition of photography in theswitching/inflection range also form part of this system.

[0119] Although FIG. 9C depicts a shift in which the second zoom path ismade essentially connected, the amount of shifting “up” does not need tofully align the curve to be made smoother, but need only take up aportion of the discontinuity (e.g., reducing any inflection to aselected amount, such as an imperceptible amount). In the followingdescription, it is noted that cam groove 44 f is essentially withoutdiscontinuity or inflection, relating to the second group zoom path inFIGS. 9A-9C, and that cam groove 44 r has a small inflection, relatingto the third group zoom path in FIGS. 9A-9C. However, the adaptationdepicted in FIGS. 9B and 9C can be used for any of the systems depictedin FIGS. 1-7 or variations thereof.

[0120] It can be decided to use at least one smooth or uninflected linefor various reasons, including simplicity of movement, simplicity ofmanufacturing, or to improve exterior appearance of movement of lensbarrels (e.g., to avoid visible discontinuity in the operation of thelens barrels, so that an unsophisticated operator does not becomeconcerned about the proper operation of the camera). In the examplegiven, the movement of the lens barrel supporting the second lens groupis essentially continuous, while the switching movement of the firstlens group and the inflected movement of the third lens group cannot beseen from the exterior of the camera.

[0121] In each of the above-described embodiments, the first variablelens group 10 in FIGS. 1, 8, and 9A-9C, the second variable lens group20 in FIG. 2, the second variable lens group 20 in FIG. 3, the firstvariable lens group 10 in FIG. 4, the first variable lens group 10 inFIG. 5, the first variable lens group 10 in FIG. 6, and the firstvariable lens group 10 in FIG. 7 (including the first lens L1 and thethird lens L3 as a unit) are each switching lens groups which serve asfocusing lens groups in any focal length range.

[0122] A preferred embodiment will now be described in which the presentinvention has been applied to the zoom lens barrel in the examples shownin FIGS. 1, 8, and 9A-9C, which have a first variable lens group 10(switching lens group) and a second variable lens group 20.

[0123]FIGS. 10 through 31 show an embodiment of a zoom lens barrel(system). Unlike the zoom lens systems shown in FIGS. 1, 8 and 9, inwhich one of the first and second sub-lens groups S1 and S2, whichtogether form a switching lens group 10, is fixed to the first lensgroup frame 11, the first and second sub-lens groups S1 and S2 in thisembodiment are both movable with respect to the switching lens groupframe in the optical axis direction. In this embodiment, a moving pathof the switching lens group frame upon zooming and a path of the firstsub-lens group S1 and the second sub-lens group S2 within the switchinglens group frame can be added to each other to give a composite zoompath, which corresponds to the zoom path shown in FIGS. 1, 8, and 9A-9C.Upon focusing, the first sub-lens group S1 and the second sub-lens groupS2 are integrally moved within the switching lens frame in the opticalaxis direction. In a photographic operation, the first sub-lens group S1and the second sub-lens group S2 are placed at a predetermined position,before the release of the shutter is started, as a result of themovement of the switching lens group frame and the movement of the firstsub-lens group S1 and the second sub-lens group S2 within the switchinglens group frame in accordance with focal length information set by anoperator (the photographer) and object distance information detected.

[0124] As shown in FIG. 10, a stationary barrel 42, which is fixed to acamera body 41, has a female helicoid 43 formed on an inner surface ofthe stationary barrel 42. A male helicoid 45, which is formed on therearmost circumference of a cam ring 44, engages with the femalehelicoid 43. Arranged outside of the stationary barrel 42 is a pinion 47which is rotated by a zooming motor 46. Gear teeth (not shown) areformed on the circumference of the cam ring 44 wherein a part of themale helicoid 45 is cut out therefor. The gear teeth, which are formedto have the same oblique direction as the lead of the male helicoid 45,engages with the pinion 47. Accordingly, the cam ring 44 advances orretreats along the optical axis direction when the cam ring 44 isrotated in either direction by the zooming motor 46 due to theengagement of the female helicoid 43 and male helicoid 45. The positionof the cam ring 44 resulting from the rotation made by the zooming motor46 is detected by focal length detecting device 46C, which can include,for example, of a code plate and a brush.

[0125] A linear guide ring 48 is supported by the cam ring 44. The guidering 48 rotates relative to the cam ring 44 and moves together with thecam ring 44 along the optical axis direction (i.e., no relativedisplacement is allowed in the optical axis direction). The guide ring48 is supported by a camera body 41 in a manner that enables the guidering 48 to move only in the optical axis direction. Arranged inside ofthe cam ring 44 in order from the front side of the cam ring 44 are aswitching lens group frame 50 (first lens group frame) which supportsthe first variable lens group 10 (i.e., the first sub-lens group S1 andsecond sub-lens group S2) and a second lens group frame 49 whichsupports the second variable lens group 20. The switching lens groupframe 50 and the second lens group frame 49 are linearly guided alongthe optical axis direction by the guide ring 48.

[0126] Cam grooves 44 f and 44 r are formed on an inner surface of thecam ring 44. The cam grooves 44 f and 44 r receive the switching lensgroup frame 50 and second lens group frame 49, respectively. FIG. 11shows an arrangement of the cam grooves 44 f and 44 r in a developedview. Three sets of the cam grooves 44 f and 44 r are formedcircumferentially with each groove spaced at equi-angular distances fromone another. Radial follower pins 50 p and 49 p are provided on theswitching lens group frame 50 and the second lens group frame 49 to bereceived in the cam grooves 44 f and 44 r, respectively.

[0127] The cam grooves 44 f and 44 r include introducing portions 44 f-aand 44 r-a for the follower pins 50 p and 49 p, retracted portions 44f-r and 44 r-r for the zoom lens system, wide-angle extremity portions44 f-w and 44 r-w, and telephoto extremity portions 44 f-t and 44 r-t,respectively. A rotational angle θ₁ is defined as the rotational anglefrom the introducing portions 44 f-a and 44 r-a to the retractedportions 44 f-r and 44 r-r, respectively. A rotational angle θ₂ isdefined as the rotational angle from the retracted portions 44 f-r and44 r-r to the wide-angle extremity portions 44 f-w and 44 r-w,respectively. A rotational angle θ₃ is defined as the rotational anglefrom the wide-angle extremity portions 44 f-w and 44 r-w to thetelephoto extremity portions 44 f-t and 44 r-t, respectively. Arotational angle θ₄, defined as the rotational angle beyond thetelephoto extremity portions 44 f-t and 44 r-t, which serves as arotational angle for assembly use. Each of the cam grooves 44 r for thesecond lens group frame 49 has an intermediate discontinuous position fmthat corresponds to the zoom path of the second variable lens group 20as described in the embodiments in FIGS. 1, 8 and 9.

[0128] In contrast, no discontinuous position appears to exist in thecam grooves 44 f for the first variable lens group 10 between thewide-angle extremity portion 44 f-w and the telephoto extremity portion44 f-t since the change in shape (profile) of each cam groove 44 f issmooth in this area. This is because, in this embodiment, the switchinglens group frame 50 and the sub-lens group S2 are moved in such a mannerthat the positions of the sub-lens group S2 are not discontinuous in theshort-focal-length zooming range Zw and in the long-focal-length zoomingrange Zt, the two ranges extending on both sides of intermediate focallength fm in FIG. 1. A connection line CC is schematically shown inFIG. 1. The connection line CC connects the zoom path of theshort-focal-length zooming range Zw to zoom path of thelong-focal-length zooming range Zt, the two ranges extending on bothsides of the intermediate focal length fm. The cam groove 44 f is shapedto correspond to the zoom path connected by the connection line CC. Asthe follower pin 50 p moves along a section corresponding to theconnection line CC, the sub-lens group S1 moves from the object-sidemovement extremity to the image-side movement extremity. It is necessaryto control the zoom lens barrel so that the section of the cam groove 44f corresponding to the line CC is not used as an actual zooming range ina photographic operation (i.e., the cam ring 44 is not stopped).Alternatively, the cam grove 44 f can include the discontinuous positionsimilar to that of the cam groove 44 r.

[0129] In the above-described zoom lens barrel, the cam ring 44 advancesor retreats along the optical axis while rotating as the pinion 47 isrotated via the zooming motor 46 in either direction, which causes theswitching lens group frame 50 (i.e., the first variable lens group 10)and the second lens group frame 49 (i.e., the second variable lens group20), which are guided in the optical axis direction within the cam ring44, to move in the optical axis direction along a predetermined pathdefined by the cam grooves 44 f and 44 r.

[0130] Novel features of the present embodiment reside in a supportstructure by which the first sub-lens group S1 and the second sub-lensgroup S2 are supported in the switching lens group frame 50 and thedriving structure thereof. A particular example of an arrangement withinthe switching lens group frame 50 will now be described by reference toFIGS. 12 through 31.

[0131] As shown in FIGS. 15 and 16, a front shutter retaining ring 51, arear shutter retaining ring 52, a first sub-lens group frame 53, asecond sub-lens group frame 54, an actuator ring 55, and a gear holdingring 56 are arranged within the switching lens group frame 50. The frontshutter retaining ring 51, the rear shutter retaining ring 52, and thegear holding ring 56 form a portion of the switching lens group frame50. The first sub-lens group S1 is fixed to the first sub-lens groupframe 53, and the second sub-lens group S2 is fixed to the secondsub-lens group frame 54. The first sub-lens group frame 53, the secondsub-lens group frame 54, and the actuator ring 55 are movably fitted ina central opening 51 p (see FIG. 12) of the front shutter retaining ring51. These movable members, i.e., the first sub-lens group frame 53, thesecond sub-lens group frame 54, and the actuator ring 55, enable thefirst sub-lens group S1 and the second sub-lens group S2 to be at amutually close position, or be at a mutually distant position, withrespect to the optical axis direction, and also enable the firstsub-lens group S1 and the second sub-lens group S2 to perform focusing.

[0132] The actuator ring 55 is rotatably supported between the front andrear shutter retaining rings 51 and 52 with the rearmost portion of theactuator ring 55 being restricted by a receiving surface 52 a (FIGS. 13,15, and 16) of the rear shutter retaining ring 52. The actuator ring 55is a driving member that enables the first sub-lens group S1 and thesecond sub-lens group S2 to become mutually close or mutually distantfrom each other, and enables the first and the second sub-lens groups S1and S2 to perform focusing via the rotation thereof. The gear holdingring 56 is fixed to the front end of the front shutter retaining ring51, and a lens shutter mechanism 57 and a diaphragm mechanism 58 aresupported by the rear shutter retaining ring 52 (FIGS. 12, 15, and 16).

[0133] The first sub-lens group frame 53 has a cylindrical shape and hastwo linear guide ribs 53 a on its periphery at the opposite sidesthereof at an equi-angular interval of 180 degrees. A guide bore 53 b isformed in the guide rib 53 a. A guide rod 59 is loosely inserted (ormoveably fitted) in the guide bore 53 b. The rear end of the guide rod59 is fixed in a fixing bore 56 q formed at the rearmost portion of thegear holding ring 56 while the front end of the guide rod 59 is fixed tothe front surface of the gear holding ring 56 by a bracket 60 and ascrew 61. A coil spring 62 is placed over each of the guide rod 59between the bracket 60 and the guide rib 53 a so that the coil spring 62biases the first sub-lens group frame 53 toward the second sub-lensgroup frame 54. A U-shaped recess 56 r is provided on the gear holdingring 56 so as to receive the guide rod 59 and the spring 62 (FIGS. 25through 27). The recess 56 r communicatively connects with the centralopening 51 p of the front shutter retaining ring 51. The first sub-lensgroup frame 53 can be connected to the front shutter retaining ring 51by engaging the guide ribs 53 a with the guide rods 59 of the frontshutter retaining ring 51 at two positions, wherein the guide ribs 53 aare provided on the first sub-lens group frame 53 at 180° intervalsabout the optical axis.

[0134] As shown in FIGS. 17A, 18A, 19A and 20A, the first sub-lens groupframe 53 is provided with four shift leading surfaces (shift camsurfaces) 53 c that are formed circumferentially at equi-angularintervals on the end-face of the first sub-lens group frame 53. Annularlight-blocking support ribs 53 d (see FIG. 14) are provided radiallyoutside of the shift leading surfaces 53 c over the open ends of theshift leading surfaces 53 c. FIG. 23 shows an enlarged expanded view ofone of the shift leading surfaces 53 c which is formed essentially as astraight slope having an inclination angle α with respect to acircumferential edge of the first sub-lens group 53 (i.e., with respectto a plane normal to the optical axis), and is provided with a pair offollower engaging recesses 53 e and 53 f on either end of the shiftleading surface 53 c. Each of the engaging recesses 53 e and 53 f isformed as a shallow V-shaped recess. The follower engaging recess 53 edefines a mutually distant position on the wide-angle side and thefollower engaging recess 53 f defines a mutually close position on thetelephoto side, of the first sub-lens group frame 53 and the secondsub-lens group frame 54 (i.e., the first sub-lens group S1 and secondsub-lens group S2).

[0135] As shown in FIGS. 17A, 18A, 19A and 20A, the second sub-lensgroup frame 54 is provided on its periphery with four followerprojections 54 a, each corresponding to each of the four shift leadingsurfaces 53 c of the first sub-lens group frame 53. An inclined surface54 b is provided so as to correspond to the shift leading surface 53 cof the first sub-lens group frame 53, and the follower projection 54 ais provided on the end of the inclined surface 54 b which is the closestto the shift leading surface 53 c. The tip of the follower projection 54a has a substantially semi-circular shape which is symmetrical withrespect to the longitudinal axis thereof, so that the shapes of theengaging recesses 53 e and 53 f correspond to the tip shape of theprojection 54 a. Annular light-blocking support ribs 54 c are radiallyprovided on the second sub-lens group frame 54 inside the projections 54a and the inclined surfaces 54 b. The shift leading surfaces 53 c formedon the first sub-lens group frame 53 and the follower projections 54 aformed on the second sub-lens group frame 54 together form a shift cammechanism (of a lens group shift mechanism) that enables the lens-groupframes 53 and 54 either be at a mutually close position, or be at amutually distant position. As described above, the four shift leadingsurfaces 53 c of the first sub-lens group frame 53 and the fourprojections 54 a of the second sub-lens group frame 54 are spaced atequi-angular intervals. Accordingly, each of the surfaces can engagewith its respective projection at 180° intervals of a relative rotation.Given that N is the number of the shift leading surfaces 53 c or thefollower projections 54 a (four, in this embodiment) and that M is thenumber of the guide ribs 53 a of the first sub-lens group frame 53 orthe number of the guide rods 59 of the front shutter retaining ring 51(two, in this embodiment), the relationship between M and N is that M isa multiple of N, or in other words, N is a divisor of M. Thisrelationship makes it possible to select an assembly position from amongdifferent assembly positions, so that for example, an assembly positionthat provides optimum optical performance can be achieved.

[0136] Furthermore, a pair of linear guide projections 54 d are formedon the second sub-lens group frame 54 on the outer surface thereof. Theguide projections 54 d are formed at the same circumferential positionsas two of the four follower projections 54 a that are positioned on theperiphery of the second sub-lens group frame 54 at the opposite sidesthereof at an equi-angular interval of 180 degrees. Each of the guideprojections 54 d is formed at a position which is rearward with respectto the follower projection 54 a in the optical axis direction. Alsoformed on the second sub-lens group frame 54 on the outer surfacethereof are three lugs 54 e, which are spaced at equi-angular intervals,and are positioned rearward with respect to the guide projection 54 d inthe optical axis direction. As best shown in FIG. 24, each lug 54 e hasa pair of contact surfaces N1 and N2 that are spaced apart from eachother in a circumferential direction. Each lug 54 e also has a smoothcircular shaped end surface N3 that is symmetrical with respect to thecentral axis of the lug 54 e extending in the middle of the contactsurfaces N1 and N2.

[0137] As shown in FIG. 24, a pair of rotation preventing surfaces 51 aand 51 b are formed on the front shutter retaining ring 51 on the innersurface thereof, in order to define the range of rotation of the secondsub-lens group frame 54 relative to the non-rotating front shutterretaining ring 51, with respect to the guide projection 54 d of thesecond sub-lens group frame 54. The rotation preventing surfaces 51 aand 51 b come into contact with contact surfaces M1 and M2 of the guideprojection 54 d, respectively, when the second sub-lens group frame 54is rotated in either direction, thereby defining the rotational movementextremities of the second sub-lens group frame 54. A wide-angle linearguide slot 51 d is defined between the rotation preventing surface 51 aand a guide surface 51 c which comes into contact with the contactsurface M2 of the guide projection 54 d. A telephoto linear guide slot51 c is defined between the rotation preventing surface 51 b and a guidesurface 51 e which comes into contact with the contact surface M1 of theguide projection 54 d. Thus, the width of both of the wide-angle linearguide slot 51 d and the telephoto linear guide slot 51 f in thecircumferential direction corresponds to that of the linear guideprojection 54 d in the same direction. Accordingly, the guide projection54 d snugly fit in the guide slots 51 d and 51 f so as to movabletherein.

[0138] The clearance between the wide-angle linear guide slot 51 d orthe telephoto linear guide slot 51 f and the guide projection 54 d isdetermined smaller (stricter) than the clearance between the guide bore53 b of the first sub-lens group frame 53 and the guide rod 59. Thelinear guide projections 54 d are provided on the periphery of thesecond sub-lens group frame 54 on opposite sides thereof at anequi-angular interval of 180 degrees. A pair of the wide-angle andtelephoto linear guide slots 51 d and 51 f are provided on the frontshutter retaining ring 51 so that two linear guide projections 54 d canbe selectively received in the wide-angle and telephoto linear guideslots 51 d and 51 f with respect to the rotational positions thereof(i.e., at an angular interval of 180 degrees).

[0139] The actuator ring 55 has, on the front end surface thereof, threecontrol recesses 55 a that each correspond to each of the lugs 54 e ofthe second sub-lens group frame 54 (see FIG. 22). Each of the controlrecesses 55 a has a shape that is symmetrical with respect to thecentral axis extending parallel to the optical axis and includes a pairof effective surfaces 55 b and 55 c that respectively come into contactwith contact surfaces N1 and N2. The lugs 54 e of the second sub-lensgroup frame 54 and the control recesses 55 a constitute a focusing cammechanism of a focusing mechanism. The control recess 55 a also includesa pair of focus leading surfaces 55 d and 55 e (focus cam surfaces) onthe telephoto side and on the wide-angle side, respectively. The focusleading surfaces 55 d and 55 e each come into contact with the circularend surface N3 of the lug 54 e. The telephoto-side focus leading surface55 d and the wide-angle-side focus leading surface 55 e are providedbetween the effective surfaces 55 b and 55 c in the form of an end-facedcam having an open front end. The slopes of the leading surfaces 55 dand 55 e have opposite directions with respect to the circumferentialdirection thereof, but have the same absolute value, i.e., the slopesboth incline forwards in the optical axis direction. Annularlight-blocking support ribs 55 f (see FIG. 13) are provided radiallyoutside, and over the front portion, of the control recess 55 a of theactuator ring 55. The focus leading surfaces 55 d and 55 e, togetherwith the lug 54 e provided on the second sub-lens group frame 54, form afocus cam mechanism. As described above, the three lugs 54 e of thesecond sub-lens group frame 54 and the three control recesses 55 a ofthe actuator ring 55 are spaced at equi-angular intervals. In theillustrated embodiment, each of the lugs can engage with a respectiverecess at 120° angular intervals.

[0140] The aforementioned coil springs 62, which bias the first sub-lensgroup frame 53 rearward, so that the shift leading surfaces 53 c contactthe follower projections 54 a, and the lugs 54 e of the second sub-lensgroup frame 54 contact the telephoto side or wide-angle side focusleading surfaces 55 d or 55 e of the actuator ring 55. As describedabove, the rear end surface of the actuator ring 55 abuts the receivingsurface 52 a of the rear shutter retaining ring 52. Accordingly, thefirst sub-lens group frame 53, the second sub-lens group frame 54, theactuator ring 55, and the rear shutter retaining ring 52 (receivingsurface 52 a) can be held in contact by the sole force exerted by thecoil springs 62. As can be clearly seen from FIGS. 15 and 16, when thefirst sub-lens group frame 53, the second sub-lens group frame 54, theactuator ring 55, and the rear shutter retaining ring 52 are inengagement with each other, the front end of the second sub-lens groupframe 54 is positioned inside the first sub-lens group frame 53, and theactuator ring 55 is situated on the periphery of the second sub-lensgroup frame 54.

[0141]FIG. 21(A through H) shows the manner in which the first sub-lensgroup frame 53 and the second sub-lens group frame 54 (i.e., the firstsub-lens group S1 and the second sub-lens group S2) are moved via theeffective surfaces 55 b and 55 c between a mutually close position onthe telephoto side and a mutually distant position on the wide-angleside. Note that, solid line arrows represent the rotational direction ofthe actuator ring 55, in FIG. 21.

[0142] The arrangement shown in FIG. 21 (A) is the mutually distantposition on the wide-angle side, in which the effective surface 55 b ofthe actuator ring 55 abuts the lug 54 e, and the linear guide projection54 d of the second sub-lens group frame 54 is disengaged from thewide-angle linear guide slot 51 d. As the actuator ring 55 rotates in aclockwise direction (i.e., moves to the right in FIG. 21), the effectivesurface 55 b biases the contact surface N1 of the lug 54 e to rotate thesecond sub-lens group frame 54 clockwise (to the right in FIG. 21) untilthe linear guide projection 54 d abuts the rotation preventing surface51 b (FIGS. 21(A) through 21(C)). During the rotation of the actuatorring 55 and the second sub-lens group frame 54, the first sub-lens groupframe 53 (i.e., the first sub-lens group S1) follows the shift leadingsurface 53 c, and the follower projection 54 a of the second sub-lensgroup frame 54 so that the first sub-lens group frame 53 linearly movescloser to the second sub-lens group frame 54 (i.e., the second sub-lensgroup S1) (FIG. 21(B)). Ultimately, the follower projection 54 a engageswith the follower engaging recess 53 f and rearward movement of thefirst sub-lens group frame 53 with respect to the second sub-lens groupframe 54 in the optical axis direction is stopped (FIG. 21(C)). Sincethe follower projections 54 a and the follower engaging recesses 53 fare spaced at equi-angular intervals therebetween, eccentricity betweenthe first sub-lens group frame 53 and the second sub-lens group frame 54is prevented, with all of the projections and the recesses inengagement. This completes the switching from the mutually distantposition on the wide-angle side to the mutually close position on thetelephoto side, resulting in the first sub-lens group S1 being in amutually close position with respect to the second sub-lens groupS2(i.e., mutually close extremity). Note that the actuator ring 55cannot rotate further in this direction.

[0143] Upon completion of switching to the mutually close position onthe telephoto side, the rotation of the actuator ring 55 is reversed.The lug 54 e (i.e., the second sub-lens group frame 54) moves rearwardfollowing the telephoto side focus leading surface 55 d until the linearguide projection 54 d engages with the telephoto linear guide slot 51 f.This allows the linear projection 54 d to move only in the optical axisdirection (FIG. 21(D)). Focusing is carried out on the telephoto sidefrom the intermediate focal length to the long focal length extremity,with the second sub-lens group frame 54 and the first sub-lens group 53being moved integrally at the mutually close position via the telephotoside-focus leading surface 55 d.

[0144] Once the actuator ring 55 is rotated until the effective surface55 c abuts the contact surface N2 of the lug 54 e, the linear guideprojection 54 d of the second sub-lens group frame 54 disengages fromthe telephoto linear guide slot 51 f (FIG. 21(E)).

[0145] At this point, the rotation of the actuator ring 55 has beenreversed (upon or after completion of the switching to the mutuallyclose position on the telephoto side). As the actuator ring 55 rotatescounterclockwise (i.e., moves to the left in FIG. 21), the effectivesurface 55 c biases the contact surface N2 of the lug 54 e to rotate thesecond sub-lens group frame 54 leftward until the contact surface M1 ofthe linear guide projection 54 d abuts the rotation preventing surface51 a (FIGS. 21 (F) and 21 (G)). During the rotation of the actuator ring55 and the second sub-lens group frame 54, the first sub-lens groupframe 53 follows the shift leading surface 53 c and the followerprojection 54 a of the second sub-lens group frame 54 so that the firstsub-lens group frame 53 linearly moves away from the second sub-lensgroup frame 54. Ultimately, the follower projection 54 a engages withthe follower engaging recess 53 e and forward movement of the firstsub-lens group frame 53 with respect to the second sub-lens group frame54 in the optical axis direction is stopped (FIG. 21(G)). Since thefollower projections 54 a and the follower engaging recesses 53 f arespaced at equi-angular intervals therebetween, eccentricity between thefirst sub-lens group frame 53 and the second sub-lens group frame 54 isprevented, with all of the projections and the recesses in engagement.This completes the switching from the mutually close position on thetelephoto side to the mutually distant position on the wide-angle side,resulting in the first sub-lens group S1 being in a mutually distantposition with respect to the second sub-lens group S2 (i.e., mutuallydistant extremity). Note that the actuator ring 55 cannot rotate furtherin this direction.

[0146] Upon completion of switching to the mutually distant position onthe wide-angle side, the rotation of the actuator ring 55 is reversed.The lug 54 e (i.e., the second sub-lens group frame 54) moves rearwardfollowing the wide-angle side focus leading surface 55 e until thelinear guide projection 54 d engages with the wide-angle linear guideslot 51 d. This allows the linear projection 54 d to move only along thedirection of the optical axis (FIGS. 21(G) and 21(H)). Focusing iscarried out on the wide-angle side from the intermediate focal length tothe short focal length extremity, with the second sub-lens group frame54 and the first sub-lens group frame 53 being moved integrally at themutually distant extremity via the wide-angle side focus leading surface55 e.

[0147] Once the actuator ring 55 is rotated until the effective surface55 c abuts the contact surface N1 of the lug 54 e, the linear guideprojection 54 d of the second sub-lens group frame 54 disengages fromthe wide-angle linear guide slot 51 d, and the positions of the firstsub-lens group frame 53 and the second sub-lens group frame 54 returnback to the position shown at FIG. 21(A).

[0148]FIG. 22 shows the principle of how the focusing is carried out viathe telephoto side-focus leading surface 55 d and the wide-angleside-focus leading surface 55 e. As the actuator ring 55 is rotated in atelephoto side focusing range pt (from an infinite photographic distance∞ to a minimum photographic distance (object at a minimum distance) n),with the circular end surface N3 of the lug 54 e in contact with thetelephoto side focus leading surface 55 d, the second sub-lens groupframe 54 (whose rotation is confined by the linear guide projection 54 dwhich is in engagement with the telephoto linear guide slot 51 f) andthe first sub-lens group frame 53 (i.e., the first sub-lens group S1 andthe second sub-lens group S2) integrally moves forwardly or rearwardlyalong the optical axis to thereby carry out focusing. Similarly, as theactuator ring 55 is rotated in a wide-angle side focusing range pw (froman infinite photographic distance ∞ to a minimum photographic distance(object at a minimum distance) n), with the circular end surface N3 ofthe lug 54 e in contact with the wide-angle side focus leading surface55 e, the second sub-lens group frame 54 (whose rotation is confined bythe linear guide projection 54 d which is in engagement with thewide-angle linear guide slot 51 d) and the first sub-lens group frame 53(i.e., the first sub-lens group S1 and the second sub-lens group S2)integrally moves forwardly or rearwardly along the optical axis toprovide focusing.

[0149] In particular, focusing on the telephoto side and focusing on thewide-angle side are achieved by controlling the number of pulses countedby a encoder 64 p (see FIG. 30) provided in a driving system whichdrives the actuator ring with respect to a reference position at whichthe linear guide projection 54 d of the second sub-lens group frame 54comes into contact with the rotation preventing surface 51 a or 51 b(i.e., the position where the rotation of the actuator ring 55 isreversed). For example, the number of pulses of the driving systemrequired to move the focusing lens groups (i.e., the sub-lens groups S1and S2) from a reference position to a position corresponding to aminimum photographic distance n, to a position corresponding to aninfinite photographic distance ∞, and to a position corresponding to anintermediate photographic distance can be predetermined by taking theleading angles for the focus leading surfaces 55 d and 55 e intoconsideration. Accordingly, focusing can be properly carried out inaccordance with the object distance information by managing the numberof the pulses of the encoder.

[0150] Also, in the illustrated embodiment, the slopes of the telephotoside focus leading surface 55 d and the wide-angle side focus leadingsurface 55 e of the actuator ring 55 have opposite directions withrespect to the circumferential direction thereof, but have the sameabsolute value, i.e., the slopes both incline forwards in the opticalaxis direction, and the lug 54 e is shaped to be symmetrical withrespect to the central axis extending in the middle of the contactsurfaces N1 and N2 which are circumferentially spaced apart from eachother. Accordingly, focusing can be carried out on the telephoto side inthe same manner as on the wide-angle side. This facilitates focusingcontrol.

[0151]FIGS. 17A and 17B show an arrangement of the first sub-lens groupframe 53, the second sub-lens group frame 54, the actuator ring 55, andthe front shutter retaining ring 51 when the first sub-lens group frame53 (i.e., the first sub-lens group S1) and the second sub-lens groupframe 54 (i.e., the second sub-lens group S2) are in the mutuallydistant position at the wide-angle side, and are in a position so as tofocus on an object at infinity. FIGS. 18A and 18B show an arrangement ofthe first sub-lens group frame 53, the second sub-lens group frame 54,the actuator ring 55, and the front shutter retaining ring 51 when thefirst sub-lens group frame 53 and the second sub-lens group frame 54 arein the mutually distant position on the wide-angle side, and are in aposition so as to focus on an object at a minimum distance. FIGS. 19Aand 19B show an arrangement of the first sub-lens group frame 53, thesecond sub-lens group frame 54, the actuator ring 55, and the frontshutter retaining ring 51 when the first sub-lens group frame 53 and thesecond sub-lens group frame 54 are in the mutually close position on thetelephoto side, and are in a position so as to focus on an object atinfinity. FIGS. 20A and 20B show an arrangement of the first sub-lensgroup frame 53, the second sub-lens group frame 54, the actuator ring55, and the front shutter retaining ring 51 when the first sub-lensgroup frame 53 and the second sub-lens group frame 54 are in themutually close position on the telephoto side, and are in a position soas to focus on an object at a minimum distance. The first sub-lens groupframe 53, the second sub-lens group frame 54, the actuator ring 55, andthe front shutter retaining ring 51 are shown separated in the opticalaxis direction in FIGS. 17A, 18A, 19A and 20A, and are shown inoperation in FIGS. 17B, 18B, 19B and 20B.

[0152] Gear teeth 55 g are formed over a circumference on the rear-endperiphery of the actuator ring 55. As shown in FIGS. 12, 29 and 30, thegear teeth 55 g engage with a series of reduction gears 63 a. The seriesof reduction gears 63 a are rotated in either direction by abi-directional motor 64 which also includes the encoder 64 p. The seriesof reduction gears 63 a are held between the front shutter retainingring 51 and the gear holding ring 56, and the bi-directional motor 64 isheld by the rear shutter retaining ring 52. The gear teeth 55 g of theactuator ring 55, which are formed over the entire periphery thereof,makes it easy for the three control recesses 55 a to engage with thethree lugs 54 e of the second sub-lens group frame 54 at differentrelative rotational positions that are separated by 120°.

[0153] The lens shutter mechanism 57 and the diaphragm mechanism 58 aremounted on the rear shutter retaining ring 52. In particular, as shownin FIGS. 12, 15 and 16, the lens shutter mechanism 57 includes a shuttersector support plate 57 a, three shutter sectors 57 b, and a shutterdrive ring 57 c for opening and closing the shutter sectors 57 b. Thediaphragm mechanism 58 includes a diaphragm sector support plate 58 a,three diaphragm sectors 58 b, and a diaphragm drive ring 58 c foropening and closing the diaphragm sectors 58 b. These components areretained in the rear shutter retaining ring 52 by a sector holding ring57 d. The shutter sector 57 b and the diaphragm sector 58 b include apair of dowels. One of the dowels is rotatably supported by the supportplates 57 a and 58 a and the other is rotatably fitted to the driverings 57 c and 58 c. The lens shutter mechanism 57 opens and closes anaperture formed by the shutter sectors 57 b as the shutter drive ring 57c is rotated. The diaphragm mechanism 58 varies the size of an apertureformed by the diaphragm sectors 58 b as the diaphragm drive ring 58 c isrotated.

[0154] Sector gear teeth 57 g are formed on a part of the periphery ofthe shutter drive ring 57 c and engage with a series of reduction gears63 b that are sequentially arranged from a shutter drive motor 57 m (seeFIG. 12). When the shutter drive motor 57 m is rotated in eitherdirection, the aperture, which has been closed by the shutter sectors 57b, is momentarily opened and is then closed again. In the zoom lensbarrel of the illustrated embodiment, the shutter sectors 57 b serveboth as a variable diaphragm to provide an aperture of an arbitrarysize, and as a shutter. The shutter sectors 57 b are electricallycontrolled so that the size of the aperture of the shutter sectors 57 b(aperture value) and the length of time during which the aperture isleft opened (i.e., shutter speed) can be varied depending on theexposure, upon the release of the shutter. Furthermore, the diaphragmdrive ring 58 c includes a lug 58 g on the periphery thereof. The lug 58g engages with a diaphragm-controlling cam slot 48 s formed on an innersurface of the linear guide ring 48 (see FIG. 10). Upon zooming, thelinear guide ring 48 and the rear shutter retaining ring 52 (i.e., thediaphragm drive ring 58 c) moves relative to each another in the opticalaxis direction. This causes the lug 58 g to follow thediaphragm-controlling cam slot 48 s so as to move in the circumferentialdirection. This in turn causes the diaphragm drive ring 58 c to rotateand, as a result, the size of the aperture formed by the diaphragmsectors 58 b is varied. The diaphragm sector 58 b is provided torestrict the maximum value of the aperture diameter especially in thewide-angle side photographing range, and the degree of opening of theaperture is mechanically varied in accordance with the amount ofextension of the zoom lens barrel.

[0155] As shown in FIG. 31, the zooming motor 46 for the cam ring 44,the bi-directional motor 64 for the actuator ring 55, and the shutterdrive motor 57 m for the lens shutter mechanism 57 are controlled by acontrol circuit (control device) 66. Focal length information 67, whichis set by the user (photographer) via a zoom switch or the like,detected object distance information 68, object brightness information69, information on rotational positions of the cam ring 44, which isprovided by a focal length detecting device 46C, and information onrotational positions of the motor 64, which is provided by the encoder64 p, are inputted to the control circuit 66. The zooming motor 46, thebi-directional motor 64 and the shutter drive motor 57 m are controlledaccording to the inputted information so that exposure is carried outunder proper exposure conditions in accordance with the predeterminedfocal lengths. While the shutter sectors 57 b serve both as a shutterand as a variable diaphragm, and the diaphragm sectors 58 b restrict theaperture diameter upon photographing on the wide-angle side in thisembodiment, the diaphragm sectors 58 b can be provided as a motor-drivenvariable diaphragm mechanism.

[0156] In the illustrated embodiment, the focal length detecting device46C (i.e., a rotational position detecting device for the cam ring 44)detects rotational positions of the cam groove 44 f which correspond tothe connection line CC (see FIG. 1), such that the control circuit 66does not allow the cam ring 44 to stop in this section. If the zoom lenssystem is provided as a step zoom lens, positions at which the cam ring44 stops are controlled in a stepwise manner. As described above, whilethe operations, corresponding to the preset focal length, distance tothe object, and the brightness of the object, of the zoom lens barrel(i.e., photographing optical system) having the above-describedswitching lens group can be completed immediately before the shutter isreleased, the focal length set by an operator can be confirmed via aseparate finder optical system (not shown) that is provided separatefrom the photographing optical system.

[0157] In the zoom lens barrel using the lens barrel for the switchinglens groups, positions at which the switching lens group frame 50, thefirst sub-lens group frame 53, and the second sub-lens group frame 54stop upon a photographic operation can be practically determined in astepwise manner along the zoom path.

[0158] Note that, while the lens support/drive structure has beendescribed with regard to the first variable lens group 10 shown in FIGS.1, 8 and 9, the mechanical construction of the above-described lensbarrel is also applicable to the second variable lens group 20 in FIG.2, the second variable lens group 20 in FIG. 3, the first variable lensgroup 10 in FIG. 4, the first variable lens group 10 in FIG. 5, thefirst variable lens group 10 in FIG. 6, and the first variable lensgroup 10 in FIG. 7 (the first lens L1 is integrally formed with thethird lens L3).

[0159] In the above-described zoom lens barrel, an end-faced cam is usedfor moving the switching lens group 10 to switch between the mutuallydistant position on the wide-angle side and the mutually close positionon the telephoto side, and for making the switching group 10 perform afocusing action when the switching lens group 10 assumes the mutuallyclose position or the mutually distant position. In particular, theshift leading surfaces (shift cam surfaces) 53 c formed on the rear endsurface of the first sub-lens group frame (first ring body) 53 and thefollower projections (shift follower projections) 54 a of the secondsub-lens group frame (second ring body) 54 engaged with the shiftleading surfaces 53 c together serve as the shift cam mechanism formoving the first sub-lens group S1 and the second sub-lens group S2 tothe mutually close position and to the mutually distant position.Furthermore, the telephoto side focus leading surfaces (shift camsurfaces; focus cam surfaces) 55 d and the wide-angle side focus leadingsurfaces (shift cam surfaces; focus cam surfaces) 55 e formed on thefront end surface of the actuator ring (rotating mechanism/first ringbody) 55, and the lugs (follower projections/focusing followerprojections) 54 e together serve as the focusing mechanism forintegrally moving the first sub-lens group S1 and the second sub-lensgroup S2 to the mutually close position or to the mutually distantposition in the optical axis direction while maintaining the distancebetween the sub-lens groups (in the mutually close position or themutually distant position). Note that the first and second sub-lensgroup frames 53 and 54 together constitute a focusing lens supportmember.

[0160] As shown in FIG. 13, the annular light-blocking support ribs(annular ribs) 53 d and 55 f are provided on the first sub-lens groupframe 53 and the actuator ring 55, respectively, with each of firstsub-lens group frame 53 and the actuator ring 55 having leading surfacesformed as an end-faced cam. The annular light-blocking support ribs 53 dand 55 f are formed radially outside the shift leading surfaces 53 c andthe focus leading surfaces 55 d and 55 e, respectively, and extendtoward the second sub-lens group frame 54 over the follower projections54 a and the lugs 54 e with which the leading surfaces engage. Thesecond sub-lens group frame 54 is constructed as an end-faced followerin which the follower projections 54 a are formed on the front endsurface at positions opposite to the shift leading surfaces 53 c on thefirst sub-lens group frame 53. The annular light-blocking support rib(annular rib) 54 c is formed on the second sub-lens group frame 54radially inside the follower projections 54 a and extends toward thefirst sub-lens group frame 53.

[0161] The effect as well as the advantages of the annularlight-blocking support ribs 53 d, 54 c and 55 f will now be describedwith regard to the relationship between the first sub-lens group frame53 and the second sub-lens group frame 54. It should be appreciated bythose skilled in the art that while the annular light-blocking supportribs 53 d are provided on the first sub-lens group frame 53 for two ofthe four shift leading surfaces 53 c on the outer side thereof, the ribs53 d can be provided for all of the four shift leading surfaces 53 c onthe outer side thereof.

[0162] As shown in FIGS. 17 through 20, the annular light-blockingsupport rib 53 d provides an extension in the vicinity of the rear endof the first sub-lens group frame 53 and reinforces the first sub-lensgroup frame 53. Similarly, the annular light-blocking support rib 54 cprovides an extension of the cylindrical portion at the front of thesecond sub-lens group frame 54 and reinforces the second sub-lens groupframe 54.

[0163] Furthermore, the annular light-blocking support ribs 53 d and 54c provide coverings from outside the first sub-lens group frame 53 andfrom inside the second sub-lens group frame 54, respectively. Thisimproves the ability for the first sub-lens group frame 53 and thesecond sub-lens group frame 54, each supporting an optical system (i.e.,the first sub-lens group S1 and the second sub-lens group S2) to shieldlight. Specifically, the annular light-blocking support ribs 53 d and 54c overlap each other both when the first sub-lens group frame 53 and thesecond sub-lens group frame 54 are in the mutually distant position asshown in FIGS. 17 and 18 and when the two sub-lens group frames 53 and54 are in the mutually close position as shown in FIGS. 19 and 20. Inthis manner, the light is prevented from passing through the spacebetween the shift leading surface 53 c of the first sub-lens group frame53 and the inclined surface 54 b of the second sub-lens group frame 54.

[0164] As shown in FIGS. 15 and 16, the annular light-blocking supportrib 53 d, the inner surface of which remains in contact with part of theouter surface of the second sub-lens group frame 54, also serves as aguide when the first sub-lens group frame 53 and the second sub-lensgroup frame 54 are moved relative to each other to the mutually distantposition on the wide-angle side or to the mutually close position on thetelephoto side. Similarly, the annular light-blocking support rib 54 c,the outer surface of which remains in contact with part of the innersurface of the first sub-lens group frame 53, serves as the same guide.As a result, the stability of the first sub-lens group frame 53 and thesecond sub-lens group frame 54 in movement is improved and the sub-lensgroups S1 and S2 are prevent from inclining with respect to each other.

[0165] The annular light-blocking support rib 55 f of the actuator ring55 essentially has the same function as the annular light-blockingsupport ribs 53 d and 54 c. Namely, the annular light-blocking supportrib 55 f provides an extension of the front end of the actuator ring 55to reinforce the actuator ring 55 in the vicinity of the rib 55 f.

[0166] As shown in FIGS. 17 to 20, the annular light-blocking supportrib 55 f extends over part of the outer surface of the second sub-lensgroup frame 54 and thus prevents harmful light from entering the insideof the second sub-lens group frame 54.

[0167] In addition, as shown in FIGS. 15 and 16, one end surface of thelug 54 e of the second sub-lens group frame 54 is in contact with theinner surface of the annular light-blocking support rib 55 f and remainsin contact therewith as the end surface of the lug 54 e slides on theinner surface of the annular light-blocking support rib 55 f while thesecond sub-lens group frame 54 is moved relative to the actuator ring55. Three lugs 54 e are provided at different positions in thecircumferential direction so that they come into contact with theannular light-blocking support rib 55 f to prevent the second sub-lensgroup frame 54 from inclining. In other words, the annularlight-blocking support rib 55 f also serves as a guide for ensuring thestable movement of the second sub-lens group frame 54.

[0168] As described above, the lens barrel of the present inventionachieves reinforced ring bodies including lens group frames by providingthe annular ribs that extend over end-faced cam portions. The annularribs also improve the ability of the ring body to shield the light whenthe ring body is a lens group frame supporting an optical system.Further, the annular ribs may serve as a guide for guiding the ringbodies when the inner surface of the annular rib is formed to slide onthe outer surface of the ring body provided with follower projectionswhile remaining in contact therewith. In other words, the presentinvention provides a shift mechanism as well as a lens displacementmechanism that has improved strengths and light-shielding ability whiletaking advantage of simple construction of end-faced cam mechanisms.

[0169] However, the present invention is not limited to the embodiment.For example, while the present invention is particularly suitable foruse with lens barrels that include a switching lens group of the typedescribed above, it is also applicable to a shift mechanism other thanthose used in lens barrels for moving ring components toward and awayfrom each other.

[0170] Furthermore, obvious changes may be made in the specificembodiments of the present invention described herein, suchmodifications being within the spirit and scope of the inventionclaimed. It is indicated that all matter contained herein isillustrative and does not limit the scope of the present invention.

What is claimed is:
 1. A shift mechanism for shifting two ring members,said shift mechanism comprising: a first ring body and a second ringbody which can be rotated relative to each other about a common axis, atleast one of said first and second ring bodies being movable in adirection of said common axis; a shift cam surface formed on said firstring body on an end surface thereof which faces said second ring body,said shift cam surface being inclined with respect to a circumferentialdirection of said first ring body; a follower projection formed on saidsecond ring body for engaging with said shift cam surface; and arotating mechanism for rotating said first and second ring bodiesrelative to each other; wherein said shift cam surface and said followerprojection are arranged to move said first and second ring bodies towardand away from each other in the axial direction as said first and secondring bodies are rotated relative to each other; and wherein an annularrib is formed along the circumference of said first ring body radiallyoutside said shift cam surface to extend toward said second ring bodyover said follower projection of said second ring body.
 2. The shiftmechanism according to claim 1, wherein an inner surface of said annularrib of said first ring body is slidably in contact with a portion of anouter surface of said second ring body.
 3. The shift mechanism accordingto claim 1, wherein said follower projection is formed on said secondring body on one end surface thereof which faces said first ring body,and a second annular rib, which differs from said annular rib of saidfirst ring body, is formed along the circumference of said second ringbody radially inside said follower projection to extend toward saidfirst ring body.
 4. The shift mechanism according to claim 1, whereinsaid first and second ring bodies comprise a first sub-lens group frameand a second sub-lens group frame for supporting a first sub-lens groupand a second sub-lens group, respectively, said first and secondsub-lens groups functioning optically in a mutually close position andin a mutually distant position, with respect to the optical axisthereof.
 5. The shift mechanism according to claim 1, wherein one ofsaid first and second ring bodies comprises a focusing lens supportmember for supporting a focusing lens group so as to move in the axialdirection; and wherein the other of said first and second ring bodiescomprises an actuator ring that can rotate relative to said focusinglens support member, the rotation of said actuator ring causing saidfocusing lens support member to move in the axial direction via saidshift cam surface and said follower projection.
 6. The shift mechanismaccording to claim 5, wherein said focusing lens support member includesa first sub-lens group frame and a second sub-lens group frame whichsupport a first sub-lens group and a second sub-lens group,respectively, and are able to rotate and move in the axial directionwith respect to each other, said first and second sub-lens groupsfunctioning optically in a mutually close position and in a mutuallydistant position, with respect to the optical axis thereof.
 7. A lensdisplacement mechanism comprising: a first sub-lens group and a secondsub-lens group functioning optically in a mutually close position and ina mutually distant position, with respect to the optical axis thereof; afirst sub-lens group frame and a second sub-lens group frame whichsupport said first sub-lens group and said second sub-lens group,respectively, said first and second sub-lens group frames beingrotatable about a common axis, and movable in a direction of said commonaxis, with respect to each other; a shift cam surface formed on saidfirst sub-lens group frame on an end surface thereof which faces saidsecond sub-lens group frame, said shift cam surface being inclined withrespect to a circumferential direction of said first sub-lens groupframe; a shift follower projection formed on said second sub-lens groupframe for engaging with said shift cam surface; and an actuator ring forrotating said first and second sub-lens group frames relative to eachother; wherein said shift cam surface and said shift follower projectionare arranged to move said first and second sub-lens group frames to saidmutually close position and to the mutually distant position as saidfirst and second sub-lens group frames are rotated relative to eachother; and wherein an annular rib is formed along the circumference ofsaid first sub-lens group frame radially outside said shift cam surfaceto extend toward said second sub-lens group frame over said shiftfollower projection of said second sub-lens group frame.
 8. The lensdisplacement mechanism according to claim 7, wherein an inner surface ofsaid annular rib of said first sub-lens group frame is slidably incontact with part of an outer surface of said second sub-lens groupframe.
 9. The lens displacement mechanism according to claim 7, whereinsaid shift follower projection is formed on said second sub-lens groupframe on one end surface thereof which faces said first sub-lens groupframe, and a second annular rib which differs from said annular rib ofsaid first sub-lens group frame is formed along the circumference ofsaid second sub-lens group frame radially inside said shift followerprojection to extend toward said first sub-lens group frame.
 10. Thelens displacement mechanism according to claim 7, wherein said first andsecond sub-lens groups form one of a plurality of variable lens groupsof a zoom lens system which are moved in the optical axis directionduring zooming, said first and second sub-lens groups serving as a focuslens group when in the mutually close position and when in the mutuallydistant position, and wherein a focusing mechanism is provided formoving said first sub-lens group frame and said second sub-lens groupframe to said mutually close position and to said mutually distantposition in the optical axis direction while maintaining the distancebetween said sub-lens group frames.
 11. The lens displacement mechanismaccording to claim 10, wherein said focusing mechanism comprises: asupporting barrel for supporting said first sub-lens group frame andsaid second sub-lens group frame, said first sub-lens group frame beingsupported in a manner that allows said first sub-lens group frame tomove in the optical axis direction and prevents rotation thereof, saidsecond sub-lens group frame being supported in a manner that allows saidsecond sub-lens group frame to rotate between two rotational extremitiesover a predetermined angle and allows linear movement thereof in theoptical axis direction, while preventing rotation thereof, at tworotational extremities thereof, each of said two rotational extremitiescorresponding to said mutually close position and said mutually distantposition; a focus cam surface provided on said actuator ring on an endsurface thereof which faces said second sub-lens group frame, said focuscam surface being inclined with respect to a circumferential directionof said actuator ring; and a focusing follower projection provided onsaid second sub-lens group frame for engaging with said focus camsurface at one of said two rotational extremities, said focusingfollower projection being different from said shift follower projectionfor engaging with said shift cam surface of said first sub-lens groupframe; wherein said focus cam surface and said focusing followerprojection of said second sub-lens group frame are arranged so as tomove said second sub-lens group frame in the optical axis direction assaid actuator ring is rotated.
 12. The lens displacement mechanismaccording to claim 11, wherein a second annular rib which differs fromsaid annular rib of said first sub-lens group frame is formed along acircumference of said actuator ring radially outside said focus camsurface to extend toward said second sub-lens group frame over saidfocusing follower projection of said second sub-lens group frame.